Many vehicles are provided with auxiliary drive devices on the front wheels to provide increased traction under certain operating conditions. The recent trend has been toward the utilization of variable displacement hydraulic motors as the auxiliary drive devices. Generally, such front wheel drive arrangements are offered as optional features to a basic vehicle and ideally identical front wheel support structures are used on both the basic vehicles and those equipped with the auxiliary front wheel drive. One of the problems encountered with this approach has been that of providing a mounting arrangement which does not require extensive additional machining or elements added to the basic wheel structure so that the same basic wheel support structure design may be economically used on the basic machine.
Another problem encountered is that heretofore the hydraulic motor of the variable displacement overcenter swash plate type and its attendant shaft support bearings and seals have installed in the wheel support structure in piecemeal fashion making the initial assembly and subsequent servicing of the hydraulic motor extremely difficult.